For the ninth year in a row, the Rocky Mountain Black Conservatives marched in the Martin Luther King Jr. parade in Denver, only this time, they were followed.

Eight to 10 masked antifa activists — all of them white — shadowed the marchers, walking in step with them for the entirety of the 3.1-mile route, and eventually drawing a police escort, said RMBC executive director Derrick Wilburn, who posted a photo of the leftist protesters on Facebook.

Mr. Wilburn said the activists’ intent was to harass the group of 40 to 50 conservatives, who included members of the Denver Republican Party and supporters of Casper Stockham, a black Republican seeking the party nomination to run against Democratic Rep. Jason Crow.

“Obviously they planned this in advance,” said Mr. Wilburn. “They clearly just wanted to irritate, agitate, so they walked alongside us, in front of us, behind us, with their stupid little bandanas on. I don’t know how the Denver PD got tipped off, but they were right there, walking right alongside them as they walked alongside us.”

It was the first time the black conservatives had been targeted by antifa “punks,” he said, “but then again, antifa wasn’t really a thing until the last couple of years.”

“We just wanted to be there for the reason everyone else was there, to celebrate Dr. King and remember everything he’s done for our country,” Mr. Wilburn said. “But these knuckleheads, they can’t stand that, so there they were.”

If the antifa, short for “anti-fascists,” saw any irony with the specter of whites carrying “Black Lives Matter” signs while intimidating blacks during an MLK event, they didn’t show it, he said.

“They’re a bunch of white kids, and here they are harassing the Rocky Mountain Black Conservatives, who are marching in a parade to honor Martin Luther King,” said Mr. Wilburn, former vice chairman of the Colorado Republican Party. “They don’t get it. They can’t see the hypocrisy of their own position.”

Why did antifa follow the group? An activist who contacted The Washington Times on Tuesday said the antifa marchers were “present and keeping eyes on a group of fascist adjacent Republicans.”

“It should also be noted that yesterday antifascists only marched near Casper’s group to monitor their activities and keep the rest of the crowd safe,” said the email from “Sophie M Scholl,” who described herself as an “anti-fascist and immigrant rights activist.”

The 35th annual “Marade,” one of the largest MLK holiday parades in the nation, typically draws between 50,000 to 75,000 participants and onlookers. This year’s crowd included Denver Mayor Michael Hancock, Gov. Jared Polis and former Gov. John Hickenlooper.

Mr. Wilburn said the antifa activists stuck with the cohort of white and black conservatives and left alone the predominantly white progressive groups participating in the event.

“We should be just as able to walk in a parade, harassment-free, as the Greenpeace people or any other leftist group should,” said Mr. Wilburn. “They were clearly there to harass us. It wasn’t like it was any big secret. Any fool could have figured out what they were doing. We didn’t care.”

Antifa activists are known for engaging in “self-defense” against those they deem “fascists,” which has included physical violence, but Mr. Wilburn said they went their separate ways at the end of the parade without incident.

“Other than just being annoying, they weren’t acting like they were looking for a problem, but you never know. They all have on backpacks, and you don’t know what’s in there,” he said. “We’ve all seen the videos of them pepper-spraying people in other cities. I think it’s probably fortunate that the Denver PD were just a few steps away, or who knows what these idiots might have been capable of?”